Work is proposed on three projects involving interferon. First, we will attempt to clone an interferon gene and/or identify interferon genes in clone libraries of murine and duck DNA. Purified mouse interferon cDNA will be used as a probe for screening mouse DNA libraries for interferon genes. Any transformants found to be positive by this test will be further examined by extracting the RNA that they contain, translating it in a cell-free protein synthesizing system and testing for interferon. A library of duck DNA will also be prepared and screened for interferon genes, using the ability of RNA isolated from them to be translated into inteferon as a screen. Second, we plan to continue our studies on the effect of interferon on the multiplication of avian RNA tumor viruses. We plan to do this work using pure individual species of duck interferon, following the protocol that we have used in the past. Third, we plan to continue our search for constitutive interferon producing human cells. We have so far screened about 500 colonies that were picked from plates containing mixtures of cells and VSV. We plan to increases the selectivity of this technique by increasing the amount of VSV and using antiserum against this virus during the colony picking process. We also plan to mutagenize cells and to use various other human cell lines such as KB cells, various human fibroblast cell lines transformed with various tumor viruses, and human breast cancer cell lines, such as MCF 7 cells.